1. Field of the Invention
This invention relates to bipolar semiconductor devices and to processes for their fabrication.
2. Description of Related Art
Bipolar devices fabricated using known processes are limited in terms of performance by base resistance and capacitance. If the performance of bipolar devices is to be improved, it will be necessary to reduce the area of the base. Considerable attention has already been given to the reduction of base area and the scope for further reduction is severely limited by alignment tolerances for the base and emitter contacts and the limits of resolution of the lithographic process. Consequently there exists a need for an improved fabrication process which will enable the fabrication of bipolar devices having bases of reduced area without the need to define small device dimensions lithographically.